feat: make kvcache.Indexer as gRPC Service

[zhengkezhou1]

fix: #14

Main Changes

• Added a gRPC API specification to expose the core functionality of kvcache.Indexer as a service.
• Implemented a minimal server and client example under kv_cache_index_service to demonstrate basic usage and integration.

[zhengkezhou1]

@vMaroon please take a look.

[vMaroon]

Thanks @zhengkezhou1 - will review as soon as possible.

[Copilot]

Pull Request Overview

This PR implements a gRPC service interface for the existing kvcache.Indexer functionality, exposing it as a network service. It addresses issue #14 by creating a minimal but functional gRPC API wrapper around the core KV cache indexer.

• Added gRPC protobuf definitions for IndexerService with GetPodScores RPC method
• Implemented server and client examples demonstrating the service integration
• Updated dependencies to include gRPC and protobuf packages

Reviewed Changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
go.mod	Added gRPC and protobuf dependencies, promoted dustin/go-humanize to direct dependency
api/indexer.proto	Defines the gRPC service specification with GetPodScores method
api/indexer.pb.go	Generated protobuf Go code for message types
api/indexer_grpc.pb.go	Generated gRPC service stubs and client/server interfaces
examples/kv_cache_index_service/server/server.go	Implements IndexerService wrapping kvcache.Indexer functionality
examples/kv_cache_index_service/server/main.go	Server application with sample data initialization
examples/kv_cache_index_service/client/main.go	Client example demonstrating service usage

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[zhengkezhou1]

@vMaroon please take a look.

[vMaroon]

Sorry for the delayed review - very packed couple of weeks. Thank you for handling this!

[zhengkezhou1]

This step is mandatory; otherwise, the client will be unable to query the data. I do not understand why this is happening. As shown in the image, blockKey-4 should not exist.